Obviously to learn a language you need to know vocab, so the best way to learn it is just write out out the important words / phrases and just keep on going over them by covering them on both the Irish side and the English side. I recommend you listen to TG4 or raideo na liffe or the likes to improve listening capabilities and also oral to an extent. The most important thing in my opinion is grammar which includes loads of things. I know that in so many of the sections of the paper your Irish is worth so many marks, so having good grammar is so important and you should really focus on that. But at the same time you can't use grammar if you don't know the words so vocab is also important.. Hope this helps a bit.